One end lift



Aug. 31, 1954 Filed April imumm W. C. TRAUTMAN ET AL ONE END LIFT 7 Sheets-Sheet l IN V EN TORS g- 1954 w. c. TRAUTMAN ETAL 2,687,873

ONE END LIFT 7 Sheets-Sheet 2 Filed April 13, 1951 mm; W? @WM 5 mc a, Z W 5 7 Sheets-Sheet 3 W. C. TRAUTMAN ETAL ONE END LIFT Aug. 31, 1954 Filed April 13, 1951 Aug. 31, 1954 w. c. TRAUTMAN ETAL 2,537,873

ONE END LIFT Filed April 13, 1951 7 Sheets-Sheet 4 Eli Aug. 31, 1954 Filed April 13, 1951 W. C. TRAUTMAN EI'AL ONE END LIFT 7 Sheets-Sheet 5 g- 1954 w. c. TRAUTMAN ETAL 2,687,873

ONE END LIFT 7 Sheets-Sheet 6 Filed April 13, 1951 HQH 0169. 21421 711471 Foeri 14/ MAQZZ.

g- 1954 w. c. TRAU"I'MAN ETAL 2,687,873

ONE END LIFT 7 Sheets-Sheet 7 Filed April 13, 1951 Wife? (7 Faker? M/ M0 /Va% Patented Aug. 31, i954 ONE END LIFT Walter C. Trautman and Robert W. McNabb,

Racine, Wis., assignors to Walker Manufacturing Company of Wisconsin, Racine, Wis., a corporation of Wisconsin Application April 13, 1951, Serial No. 220,872

16 Claims.

This invention relates to portable lifting devices and, in particular, to the mobile type of lifting unit that is especially useful around garages and repair shops where it is desired to lift heavy loads quickly, easily, and safely. An important use of the invention is in lifting one end of an automobile to a height such that repair work can be easily done underneath by a mechanic in a kneelin or sitting position.

In its preferred form, the lifting unit of the invention has two primary structural members that have a jackknife relationship to each other. Thus, one of the members is a top beam that preferably carries wheels at one end and is adapted to engage an automobile or other object at its other end. The other member is a lower beam which is hinged to the top beam at one of its ends and which preferably carries wheels at its other end. The hinge connection between the members is preferably located intermediate the ends of the top member to give added stroke to the lift, though at all elevations the'line of force of the load falls between the wheel carrying ends of the members so that stability is always maintained. Thus, the top beam acts, in effect, as a lifting boom and preferably carries a pair of adjustable arms located on opposite sides of the center line of the lift which securely engage the work and avoid the possibility of eccentric loading. Suitable means, preferably a hand pump actuated hydraulic cylinder and ram assembly operating in tension, acts between the members to draw them toward each other, thus pivoting each upwardly about its Wheel carrying end. In the preferred form, this means is connected to the members so that its leverage increases with the amount of lift. In the preferred arrangement wherein the hydraulic assembly is employed to elevate the members, both hydraulic and mechanical safety lock devices are used to prevent untimely collapse of the lift, these devices bein unlocked in sequence by movement of a foot pedal. Locking means are also contemplated for the wheels at one end of the lift, preferably on the upper beam, so that walking of the unit during elevation or lowering can be avoided. While the device of this invention can lift very high, it nevertheless has an extremely low collapsed height since the lower beam and the operating mechanism fit inside of the upper beam. A caster wheel is provided to substitute for a pair of wheels at one end so that the lift can be more readily moved about, such movement of the unit as a carriage being conveniently energized by pushing or pulling the pump handle.

The foregoing and other features and advantages of the invention are described in connection with the followin drawings which have been selected to illustrate the principles of the invention:

Fig. 1 is a plan view of a preferred embodiment of the invention;

Fig. 2 is a longitudinal section taken on line 22 of Fig. 1 showing the lift in elevated position;

Fig. 3 is a plan view of the operating mechanism with parts removed and other parts broken away;

Fig. 4 is a section taken on line 4-4 of Fig. 3;

Fig. 5 is a section taken on line 5-5 of Fig. 1;

Fig. 6 is a section through the hydraulic assembly taken on line 6B of Fig. 3;

Fig. '7 is a section taken on line 1'! of Fig. 6;

Fig. 8 is a side view of the lift in collapsed condition;

Fig. 9 is a perspective view of the lift in elevated condition supportin the rear end of an automobile;

Fig. 10 is a plan view, similar to Fig. 3, of a modified form of the invention;

Fig. 11 is a section taken on line Ill| of Fig. 10; and

Fig. 12 is a section taken on line Ill-l2 of Fig. 10.

As shown best in Figs. 1 and 2, the lift has a top frame or boom member 5 which includes vertical side plates 1 that are integral with a lateral web 9 and which serves as a primary structural element as well as a housing to conceal most of the operating mechanism. The V shaped gusset I0 is welded to plates 1 and 9 imparts torsional stiffness to the boom. An axle I I is rigidly secured to the rear end of the frame 5 and may be tubular in construction as shown. The axle l I extends laterally and horizontally a substantial distance beyond each of the plates 1 and journaled on roller bearings l2 in each end thereof is a wheel [3 whereby the frame 5 is rendered mobile.

In accordance with the invention, means are provided to lock the wheels l3 against rotation. This may be accomplished in various ways a simple and preferred method being best illustrated in Fig. 5. As there shown, the wheels [3 have inside radial faces l5 that are provided with a series of radially extending, angularly spaced recesses IT. The recesses on each wheel receive a nose 19- that is clamped between the side elements 20 of bifurcated lever 2| that is pivoted on axis 23 to opposite sides of the axle ll. One of the side elements of each lever 2| has a projection 25 extending at an angle thereto and provided with an aperture 21 in which one end 3 of a U-shaped spring wire 29 is received. Ihe bight of the U-shaped wire rests against a pin 3| fixed in the 'axle II and the other end of the wire is fixed to the axle by screw 33. It is clear from Fig. 5, that as a lever 2| rocks on its axis 23 towards a wheel l3, the nose l9 enters a recess IT to lock the wheel against rotation. When a lever 2| is rocked away from its wheel 13, the nose I9 is withdrawn and the wheel is free to rotate on its bearing in the end of the axle. The aperture 21 and spring 29 are located so that the line of spring force applied to the projection 25 passes over center as the lever 2| is rocked between its two extreme positions. The springs 29 therefore serve to yieldably hold the levers 21 in either the engaged or disengaged positions. As indicated in Fig. 5, the inside of the tubular axle I I may be reinforced at the lever axis 23 by a plu 35 held in place by radial pin 31.

As is apparent from Fig. 2, the frame is elevated by upward pivoting about its rear end. The forward end of the frame 5 carries means for engaging the object to be lifted, leftand right-hand fixtures 39 and 40 adapted to engage the underside of an automobile being illustrated in Figs. 1 and 2. Each of these fixtures includes a hollow hub 42 that is. mounted on the ends of a lateral and horizontal cross bar or tube 43 which is rigidly secured to the forward end of the frame 5, preferably with its axis located above the surface of web 9. Each hub 41 has rigidly secured to it, as by welding at 45, an arm 4.? that may be formed of heavy steel plate and which extends parallel to the side plates 1. Each arm 4? has a section 49 that extends on one side of the hub 4-! and another section 5! that is on the other side of the hub, the. sections 49. and 51 preferably being laterally offset so that section 48 lies outwardly of section 5|. Sections 49 are provided with approximately semi-circular cutouts 53 that face forwardly and upwardly when the arms 4 are level. The cutouts are capable of cradling front and rear automobile axles. The hubs 4: can pivot, on the ends of the cross bar 43 to various angular positions, as shown in Fig. 2, so that the cutouts. 53 face upwardly and over the range from forwardly to rearwardly. Each hub 4! may be held in position by a in 55 that extends radially through aligned apertures 51 and 59 in the walls of the hub and cross bar 43, it being recognized that by providing both the hub and the cross with a number of angularly spaced holes for the pin 55 a wide variety of positions may be obtained. To prevent loss the pins 55 may be permanently secured to the frame 5 by chains Bl. The fixtures 39 and- 40 are also adapted to engage the underside of knee action front end suspensions. For this type of use, they are turned over so that the cutouts 53 are underneath and the relatively straight edges 53 are uppermost. The front end suspension then rests on edges 63- and weight is distributed on both sides of the cross bar 43 so that it is not necessary to use pins 55 to hold the fixtures in position. The edges 63: may be provided with ledges. 65 at the forward end to prevent elements of the automobile suspension from sliding off the edges.

As already described, the front end of the upper channel or frame 5 is the lifting end and, subject to an exception hereafter noted, it pivots about. the wheels l3- mounted at its rear end. The frame 5 is braced and supported by a lower, front, channel or lifting leg 69 that. is hinged at its rear end on trunnions H to a central portion of the frame 5. The front leg 68 is preferably of a construction similar to that of the frame 5 and has side plates 12 rigidly joined by a top and bottom webs 13. An axle 15, the same as axle H, is rigidly secured by welding or other suitable means to the front end of the leg 69. The ends of the axle 15 extend outwardly substantial distances beyond the side plates 1 I, and rotatably carry wheels 11, which for the sake of manufacturing simplicity are identical to wheels [3. Inasmuch as wheel locks are more conveniently used at the rear end of the lift, i. e., on wheels l3, there need be no locks provided for wheels 11, it being appreciated, however, that it is within the purview of the invention to reverse the wheel locking arrangements, if desired, or to provide locks for all the wheels.

The rear portion of front channel 69 fits inside of the frame 5 when the lift is collapsed and in order to. elevate. the member 5 means are provided to act between the channel 69 and the member 5 to draw their respective front and rear ends (mounted on wheels I! and (3) toward each other. Such movement is accommodated by pivoting of the channel or leg 69 on trunnions. l I. The movement is actuated by suitable means, preferably a hydraulic cylinder and ram assembly 8|.

The hydraulic assembly Bl has a cylinder 82 with a valve block 83 at its rear end. The block 83 has. a transverse aperture 84 through it to receive trunnion shaft 85 that is mounted by retainers 36 on the side plates 1 and thus pivotally supports the assembly 8! on the rear end of the frame member 5. The assembly 8! has a. ram 87 that slides in the cylinder 82. The ram is provided at its front end with a trunnion block 8-9 that pivotally receives the. trunnion shaft 9! which is mounted on the side plates 2 and which therefore pivotally mounts the assembly 8| on the front leg 69. The trunnion shaft Si is located below and forwardly of the trunnions "H so that the leverage applied by the assembly 8i increases with the amount of lift. It will be observed that in the preferred arrangement shown the pivots 85- and 9! are located unequal distances from the hinge H and that in the fully elevated position these three points define the corners of a substantially right angle triangle with the hypotenuse located between the hinge H and one of the pivots, or, in other words, the line of force of assembly 8! being an altitude. For the purpose of structural reinforcement, side arms 3 may be welded at 94 or otherwise rigidly affixed, to the side plates #2 and provided at opposite ends with bores to receive the trunnions.

The valve block 83 carries a pump 55 and adjacent the pump it has the upstanding lugs 91. A pump handle socket block 99 fits between the lugs 91 and is pivoted to them by means of the transverse pin 10!. The socket block has a roller N33 to, engage the pump piston and a suitable socket I05 to removably receive the pump handle I01 which, it will be seen, can be rotated forwardly to lie flat on the top of web 9. As will be described more fully hereinafter, the operation of the assembly 8! is such that actuation of the pump 95 causes the ram 81 to move into the cylinder 82 or toward the rear of the lift, this, of course. pulling the axles I l and 11 toward each other to elevate member 5. and fixtures 39 and 40-. Working pressure on the ram 81 is released to permit it to move out of the cylinder 82. and descent of the lift by rearward movement .the axle II.

of a release, valve lever I09 that is mounted on the valve block 83 against the resistance of a spring I I I that is connected to it and anchored at its forward end to the ram end block H3 of the cylinder 82 as shown at II5.

While the pressure in the hydraulic system is sufilcient to hold the member 5 in elevated position under load, there is always a possibility of its failure or leakage as well as a possibility that the release valve might be inadvertently tripped either of which might result in serious consequences due to lowering of the lift. In order to prevent this, a safety device is provided and this is preferably arranged so that it must be overcome prior to operation of the release valve controlled by lever I09.

A preferred form of safety device is shown in Figs. 2-4. and resides in the use of dogs or pawls H1 and rack bars H9. The rack bars II9 move with the ram 81 and have apertures I2I at their forward ends by means of which they are mounted by way of a bushing I22 on the trunnion 9| on either side of the ram trunnion block 89. Guide blocks I23 are secured to the sides of the ram end block I I3 to slidably connect them to the cylinder in desired alignment with the pawls I I1.

The pawls I I1 are secured on either side of the block II3 by radial pins I25 to a transverse rock shaft I21 which pivots in an aperture I29 in the ramend block I I3. A coil spring I3I is anchored at one end to one of the pawls II 1 and at its other end to a guide block I23 and serves to yieldably drive the pawls toward the rack bars H9. The pawls I I1 face rearwardly and when fitted in teeth I33 in the bars I I9 prevent the ram 81 from moving out of the cylinder 82 even though pressure conditions in the assembly 8I may permit such movement. A crank arm I35 is mounted on one end of the rock shaft I21 and by abutment with pin I36 extending transversely from a pawl serves as means to pivot the shaft and lift the pawls II1 out of the teeth I33. When this is done, the ram 81 may move out of the cylinder 82 and the members 5 and 69 can pivot relative to each other on shaft 1I until the lift is collapsed.

It may be noted here that in fully collapsed condition, the lift rides on front wheels 11 and on a single rear caster I31 of a conventional type that swivels in its housing I39 which is rigidly secured to the underside of web 9 forwardly of Thus, in fully collapsed condition the rear wheels I3 are off the ground and its maneuverability is enhanced by use of the caster I31. It will now be recognized that when the assembly 8| is actuated to raise the lift, the member 5 will first pivot about the caster I31. This will lower wheels I3 to the ground and further elevation will shift the pivot axis to the axis of rotation of the wheels I3, the reverse procedure occurring when the lift is lowered.

Lowering of the lift from elevated position is actuated by a control member, namely, depression 83 and is connected to assembly I53 at its bifurcated lower end so that depression of foot pedal MI moves the top of the lever toward the rear (to the left in Fig. 4) Such rearward movement of lever I5I is yieldably resisted by a spring I51 that is connected to a pin I59 extending across the bifurcated top of lever I5I. The forward end of spring I51 is anchored at I6I to a guide block I23 and the spring is preloaded so that it serves to force the foot lever I4I to its upper, released position. I

Movement of the lever I5I toward the rear when pedal MI is depressed first lifts the pawls II1 out of the teeth I 33 in the rack bar II 9 and then forces release valve lever I09 to the rear to let the ram 81 move out of the cylinder 82. The lever I5I is connected to the pawls through a spring I63 that hooks on the pin I59 and on the bottom of pawl crank I35 as shown at I65. The spring I63 is preloaded and overrides spring I3I but, its tendency to rotate the pawls II1 out of the teeth I33 is resisted by spring I51 as well as spring I3I.

The initial tension in spring I 63 plus its heavy coils permit it to act as a solid tension link so long as the forces required to remove the dogs II1 are low. Then, depression of foot pedal MI and rearward pivoting of lever I5I will result in the rotation of the pawls II1 out of the teeth 533. However, if the hydraulic system fails-with a load on the lift, the dogs I I1 transmit the load to the teeth I33 and the forces required to rotate them out of the teeth are therefore very high. Under this condition depression of foot pedal I 4! will simply be absorbed by the spring I63 and it will not be possible to remove the pawls II1 from the teeth I33 until the load in the lift is removed. Likewise, excessive force applied to the pedal I4I will not result in breakage of some parts of the mechanism as would be the case if I63 were a solid bar.

Continued depression of pedal I4I moves the lever I5I rearwardly until it strikes release valve lever I99, this engagement being delayed until the pawls are fully out of ratchet engagement with the teeth I 33. Further movement of pedal MI, and thus lever I5 I, forces the lever I09 rearwardly and, as will hereinafter appear, allows pressure on the ram 81 to be relieved at a rate proportional to the movement oflever I09. The lift therefore is collapsed at a controlled rate by its own weight or by that of a load upon it. It will be obvious that suitable limit stops may be provided, if necessary, to prevent the pawls II 1 from rotating to such an extent that spring I 3I passes over center.

It is evident that in connecting the shaft I43 to the lever I5I, the link assembly I53 joins units (member 5 and hydraulic assembly 8|) having different types of movement during elevation and descent of the lift. The frame 5 pivots about caster I31 and about wheels I3 and so does the hydraulic assembly 8|, but the assembly 8| also pivots on trunnion relative to the member 5. Thus, the lever I5I is subject to movement that shortens or lengthens its distance from the arm I 41. With the construction illustrated the lever I5I is a maximum distance from the arm I41 when the lift is fully collapsed so that elevation of the lift is accompanied by shortening of the distance. The link assembly I53 includes a rod I61 that is pivoted to the bifurcated lower end of lever I5I on a transverse pin I69. The rear end of the rod I61 slidably extends through a transverse pivot pin I1I mounted on the'bifurcated lower end of crank arm I41. A sleeve I13 and locking units I15 are threaded on, the

'end of the rod I61 and bear against the rear side of pin I1I when the lift is collapsed. It will be seen that the control of the length .of the rod I81 afforded by the nuts and sleeve I13 permits the angular position of lever II to be adjusted to regulate to its spacing from the release valve lever I09. During elevation of the lift, the shortening of the distance between lever I5! and arm I41 will result in a tendency for the sleeve I13 to move rearwardly out of contact with the pin I1I. Movement of lever I5I or lost motion because of this shortening is prevented by a coil spring I19 that is mounted on the rod I61. The spring bears at its forward end against a radial shoulder IBI on the rod I61 and at its rear end against a sleeve I83 on the rod which it presses against the pin I1 I. Shortening of the distance between the lever I5I and arm I41 compresses the spring I19 which therefore prevents the lower end of the lever I5I from moving rearwardly. The spring I19 is stiff enough so that it transmits sufficient force when the pedal MI is depressed to hold the release valve lever I09 in its rearmost position during collapse of the lift.

A stop bracket I85 is afiixed to the rear end of web 9 to determine the limit of downward motion of pedal I4I. Its upward motion is limited by abutment of lever I5I with an edge I86 of the valve block casting 83.

As already indicated, the hydraulic cylinder and ram assembly 8| is unusual in lift constructions in that its working stroke consists in moving the ram into the cylinder while in its nonused condition the ram extends as far out of the cylinder as possible. This use of the assembly enables the cylinder itself to be used as a reservoir for oil as shown best in Figs. 3 and 6-7.

The ram 81 has a piston I9I suitably affixed to its rear end and sliding in a bore I93 provided by the cylinder 82. The front and rear ends of the cylinder 82 are closed by the aforementioned ram end block I I3 and valve block 83 which may be threaded on to the end portions thereof and provided with suitable sealing means to prevent leakage. On the working stroke. high pressure exists in the space between the ram block I I3 and the front face of the piston I9I. This is provided by the pump 95 which takes the fluid from a relatively small reservoir chamber I95 in the block 83 that is in open communication through the end of the block with the low pressure space in bore I93 behind piston I9I. In flowing from reservoir I95 to the pump, oil flows through strainer I91 that is held in lateral passage I99 by a closure screw 29I threaded into block 83. Vertical passage 203 opens into and receives oil from passage I99. It is enlarged to provide valve seat 205 for ball check 201 that prevents oil from passage 203 into passage I99. Oil from the reservoir flowing upwardly in passage 203 is attracted by pump piston created suction in lateral and downward passage 209 and flows through it to the bottom of a bore 2 formed in block 83 to threadably receive pump cylinder 2I3.

The pump 95 has a plunger-piston 2I5, with suitable packing 2I1 at its working end, which is reciprocated in cylinder 2 I3. A transverse pin 2I9 in the plunger 215 slides in slots MI in the cylinder 2 I3 which therefore limit the stroke of the plunger. The plunger 2 l5 has a radial shoulder 223 against which a spring 225, surrounding cylinder 2I3, presses a tube or housing section 221. The tube 221 telescopes on another tube or housing section 229 that is pressed by spring 225, mounted therein, against radial shoulder 8 23I on the cylinder 2I3. It is clear that downward movement of the pump handle I01 on pivot IOI enables roller I03 to force the plunger 2I5 downward in cylinder 2I3 against the resistance of spring 225.

On the downward or pumping stroke of plunger 2 I5, oil is forced from cylinder 2I3 through passage 209 to passage 203. Pressure in passage 203 seats ball check 201 so that oil cannot flow to the reservoir through passage I99. Oil can flow into passage 235 which opens into passage 203 between passage 209 and valve seat 205. Passage 235 is enlarged into passage 236 to provide a seat 231 for ball check 239 which is pressed by spring I via slidable spring cup 243 against the seat. The compression of spring MI is regulated by the adjustment plug 245 that is threaded into the block. This arrangement constitutes an overload or safety valve and if pressure in line 203 exceeds the setting of spring 24!, it unseats ball check 239 and oil flows by it into lateral passage 241 that opens into bore I93 back of the piston I9I.

Oil under pressure from the pump 95 can also flow upward in passage 203 to force ball check 249 from its seat 25I formed by enlarging passage 203. It may be observed here that floating spacers 253 and 255 are put in passage 203 to keep the ball checks 201 and 249 in operative relationship to their respective valve seats. Passages 251 and 259 branch off from passage 203 which is closed at its top end by a plug 26I threaded into the block 83. Passage 251 leads the fluid to the front side of the piston whereas passage 259 leads into the release valve operated by lever I09 as will be described.

Passage 251 opens near the top of the block 83 into a horizontal, longitudinally extending passage 263. A conduit 265 is slidably received in passage 263, but sealed therein by 0 ring 261, and a spring 269, which backs up against plug 21I threaded into the block 83, presses on the end of the conduit 265 to urge it forwardly against a shoulder 213 formed in passage 215 in the ram end block II3, an 0 ring 211 or other suitable seal being provided in passage 215. Oil under pressure therefore flows from passage 251 into passage 263 and thence through conduit 285 to passage 215 in the ram end block II3. A radial passage 219 connects passage 215 with a longitudinal passage 28I opening into the rear face Of the block I I3 and thus behind the piston I9I, the packing retainer 283 shown in the drawings having suitable openings for flow of fluid through it.

Back flow from conduit is prevented, of course, by ball check 249. However, when it is desired to lower the lift by releasing pressure on the forward side of the piston I9 I, the release valve lever I09 can be rocked in a manner already described to connect the conduit to the rear side of the piston in a manner now to be described. Rearward movement of the lever I09 pivots the valve stem 285 on which it is mounted at 281. The valve stem is threaded into the block 83 as shown at 289 so that such pivotal motion causes it to also move axially. As a result, the valve 29I is moved away from its seat 293 in passage 259 by an amount proportional to the degree of pivotal motion. This permits oil to flow through passage 259 into the enlarged passage 295 containing the valve stem 285 and thence into passage 291 which opens out of the end of the block 83 behind the piston I9 I. The rate at which oil will flow by the valve end 29I depends, of course, on its spacing from the valve seat 293 and hence on the angle to which the lever I09 has been turned.

Oil is added to the cylinder 82 and reservoir I95 through a vertical passage 299 that opens into the reservoir I95 and communicates with a passage 30I that opens into the front end of the block 83 behind the piston I9I.

The operation of the lift has been indicated above in connection with each of the features of construction. From the foregoing description, it will be seen that in collapsed condition the member rests on caster I31 and the front channel 69 on wheels 11. The hydraulic assembly 8| is extended to its full length so that ram piston I9I is at the front end of cylinder 82. The lift is elevated by pumping handle I01 to actuate pump plunger 2I5. This forces oil through passages 209, 203, 251, 263, conduit 265, 215, 219, and 28! to the front side of piston I9I and drives it rearwardly to shorten the assembly 8|. Such shortening drops wheels l3 to the ground and moves wheels I3 and I1 toward each other as member 5 and channel 69 pivot toward each other on hinge II. During this movement, the rack bars II9 move with the ram 81 and pass freely by the pawls I I1.

Before elevation is begun, the fixtures 39 and 40 may be turned on cross bar 43 to the desired positions for engaging the object to be lifted. It will be noted that at all elevations the line of force of the load on the lift will pass between the front and rear axles so that the lift is stable. Actually, the line of load force approaches closer to the midpoint between the axles as the lift is elevated.

While the frame 5 is in elevated position pressure in the cylinder 82 is locked ahead of the piston I 9! to prevent collapse. As a further precaution, the dogs I I! engage teeth I33 in rack bars I I9 to prevent forward movement of the bars and thus the ram 8? to which they are connected by shaft 9I.

Lowering of the lift is actuated by depression of pedal I4I which acts through link assembly I53 to pull the bottom of lever I5I rearward. This first allows spring I53 to pull crank arm I35 rearward and rotate the pawls II'I out of the teeth in the rack bars. When the pawls are clear, the lever I5I forces lever I09 in a rearward direction to unseat valve end 29I Oil in front of the piston I9I can then flow to the back of the piston I9I via passages 23I, 2T9, conduit 265, 263, 251, 203, 259, 295, and 29'! as the weight of the lift tends to force the wheels I! and I3 apart.

During either lifting or lowering movement, the rear end of the lift may be maintained in stationary position by moving levers 2I outwardly to lock the wheels I3 against rotation.

A modified form of the invention is shown in Figs. 10-12 wherein parts essentially the same as these shown in Figs. 1-8 are referred to by the same reference numbers. The embodiment of Figs. 10-12 has a different form of lock for the rear wheels, the caster I 31 is retractible, and a slightly different connection exists between the foot lever I 4| and the pawls I.

As best shown in Fig. 10, the rear wheels 40I (corresponding to wheels I 3) have an annular brake lining 402 affixed to their inside radial face. A sleeve 403 slides on the axle II adjacent each wheel and has a radial flange engageable with the brake lining, the sleeve being fixed against rotation on the axle by suitable means such as a pin and slot connection 405. A U-shaped lever 40! has its legs pivoted on the axle I I and a cam .10 face 409 thereon engages the end of the sleeve 403 so that pivoting of the lever inwardly forces the sleeve flange against the lining 402 to lock the wheels.

In this embodiment of the invention, the foot pedal rock shaft I43 is journaled in the end of a cross shaft 4| I which, in turn, receives and is supported upon a rock shaft 4 I3 for caster pedal 4I5 which shaft pivotally extends through a side plate I. The shaft 4I3 drives shaft 4II through radial pin M5, but it is clear that the shaft 4I3 merely pivots on rock shaft I43 without turning it. The caster I3? is suitably affixed to the cross shaft lII along the center plane of the lift. This depression or elevation of pedal 4I5 will pivot shaft 4II to lower or raise caster I3'I. The pedal 4I5 may be held in depressed or elevated position by springing it under or over a catch 41? afixed to the axle II.

The pedal a rrn I4'I on rock shaft I43 drives the lever I5I through an adjustable link assembly I53 which is functionally similar to the assembly I53 described above. In this embodiment, the top of lever I 5| is connected to the pawl crank arm I 35 by a link bar 42! which is pivoted to the lever and pawl. A spring 423 anchors on pin 425 on side plate I and is connected to the bar 42I to urge it in a forward direction. It will be seen that this acts through lever I5I and assembly I53 to hold the pedal MI in elevated position. In this embodiment, the pawls III are free to pivot on rock shaft I27! except for torsion springs 427 that are anchored in the pawls and yieldably connect them to crank arms I35 which, in this case, are non-rotatably afiixed to each end of shaft I21 by virtue of non-circular opening 429. The torsion springs 42'] urge the pawls to rotate downwardly into the rack bar teeth I33. When link 42 I is pulled rearwardly due to depression of pedal MI, it rotates one arm I35 and thus shaft I2'I. The torsion springs 52'! transmit some force to the pawls tending to urge them out of the teeth and positive drive is achieved when they strike transverse pins I30 so that the pawls are lifted from the rack bars II 9. After this occurs, the lever I5I contacts the release valve lever I09 to drive it rearwardly relieving pressure on the ram 81. The lever I09 is held in closed position and at the same time spaced from lever I55 by a coil spring 43I acting between the two levers.

From the foregoing description, it will be evident that the invention provides a safe, sturdy, mobile lift that has an unusually long lifting stroke for its low startin height. Modifications can, of course, be made in the illustrative structures shown herein without departing from the spirit or scope of the invention.

What is claimed is:

1. In a portable lift, the combination of a downwardly facing channel providing an upper beam, a lower beam inside the upper and hinged at one end to the upper beam, axles with wheels secured to the outer ends of the beams to movably support them on the ground, and means acting between the beams to move said beams toward each other and thereby jackknife the beams, said last means comprising a hydraulic cylinder and ram unit wherein the ram is connected to one beam and the cylinder to the other and arranged so that the operating stroke occurs on shortening of the unit, the connection to the upper beam being adjacent its outer end and the connection to the lower beam being adjacent its hinged end, said unit being substantially completely housed inside said upper beam at all relative positions of the beams.

2. The invention set forth in claim 1 wherein the connections of said unit to the beams are arranged so that the leverage of said unit about said hinge increases with the amount of lift and the lines of centers between said hinge and the points of connection of the ram and cylinder to the beams define a triangle in which the side defined by line of centers between said points is the longest side when the lift is in collapsed condition but shortens during lift and is substantially an altitude of the triangle when the lift reaches maximum elevation.

3. In a portable lift, the combination of an upper beam, a lower beam hinged at one end to the upper beam, means for supporting the outer ends of the beams on the ground, means acting between the beams to move said outer beams toward each other and thereby jackknife the beams, said last means comprising a hydraulic cylinder and .ram unit wherein the ram is connected to one beam and the cylinder to the other, said unit including a pressure release valve, a pawl and ratchet bar assembly mounted on said cylinder and ram to prevent collapse of the lift, and common means for releasing said pawl from the bar and then operating said release valve to permit collapse of the lift.

4. In a portable lift, the combination of an upper beam, a lower beam hinged at one end to the upper beam, means for supporting the outer ends of the beams on the ground, means acting between the beams to move said outer beams toward each other and thereby jackknife the beams, said last means comprising a hydraulic cylinder and ram unit wherein the ram is connected to one beam and the cylinder to the other at points between said hinge and the respective outer ends of the beams, a ratchet bar connected to the ram and movable therewith, a pawl connected to the cylinder and engageable with the bar to prevent movement of the ram out of the cylinder, spring means urging the pawl into engagement with the bar, a control member for actuating collapse of the lift, link means operatively connecting the control member to the pawl whereby motion of the member disconnects the pawl from the bar.

5. The invention set forth in claim 4 wherein said hydraulic unit includes a pressure release valve lever and said link means operatively engages said lever only after the pawl is disconnected from the bar.

6. The invention set forth in claim 4 wherein said member is mounted on one of the beams and said link means includes a section yieldably variable in length to accommodate relative motion between the beam and unit.

'7. The invention set forth in claim 4 wherein said link means includes a link to hold the pawl out of engagement with the bar.

8. The invention set forth in claim 4 wherein said link means includes a spring to hold the pawl out of engagement with the bar, said spring exerting greater force on the pawl than said spring means, and resilient means urging the member to inoperative position and acting in opposition to said spring whereby the spring is prevented from disconnecting the pawl until the member is actuated.

9. In a portable lift having an elevating beam, the combination of a cross bar mounted on the beam and extending beyond the sides thereof, and fixtures pivotally mounted on the ends of said cross bar and adapted to engage an object to be lifted, said fixtures comprising hollow hubs slidably and pivotally mounted on the ends of said cross bar and side plates rigid with the hub and normal to the axis of the bar, said hub and bar having alignable holes therein where pins may be placed to fix the angular positions of the fixtures on the cross bar.

10. The invention set forth in claim 9 wherein said side plates extend on either side of said hub and each has a substantially straight edge on one side and an arcuate cutout in the edge on the other side, said cutout being located on one side of the axis of the hub.

11. In a portable lift, the combination of a top beam, a bottom beam fitting inside the top, a hinge connection between one end of the bottom beam and an intermediate portion of the top beam, axles at the outer ends of said beams, wheels mounted on the axles and spaced substantially outwardly from the sides of the beams, means on the inner end of the top beam for engaging a load to be lifted, said means being located between said axles, and means acting between the beams to move said axles toward each other, said load engaging means comprising a cross bar secured to said beam, and load contacting fixtures pivotally mounted on each end of the cross bar and adjustable to various angular positions about the axis of the bar, locking means forholding the fixtures in adjusted angular positions, said fixtures being located inside of the wheels and on opposite sides of the center line of the lift.

12. In a lifting mechanism having a work engaging surface, the combination of a pair of members movable relative to each other to raise or lower the work engaging surface, fluid pressure means acting between the members to supply force for moving them relative to each other, said means including a pressure release element for rendering the means inoperative, ratchet structure acting between the members to prevent relative movement thereof so as to lower the lift, and force applying means acting through a spring for applying force to the ratchet structure to render it inoperative, said spring yielding to absorb such force in the event there is a load on the ratchet structure.

13. In a portable lift, the combination of a boom, the top end of the boom being adapted to engage an object to be lifted, a leg beneath the boom and hinged to an intermediate point on the length of the boom, axles on the lower ends of the leg and boom and extending a substantial distance outwardly from the sides of the leg and boom, wheels on the ends of said axles, a variable length force applying unit pivoted at one end to the boom and at the other end to the leg and substantially completely housed within the channel shape of the boom, and a single caster wheel device secured to said boom at a point spaced inwardly of the boom axle and of greater height than the boom wheels so that upon collapse of the lift said wheels may be lifted from the ground and the boom may ride on said caster device.

14. In a portable lift, the combination of a boom, the top end of the boom being adapted to engage an object to be lifted, a leg beneath the boom and hinged to an intermediate point on the length of the boom, axles on the lower ends of the leg and boom and extending a substantial distance outwardly from the sides of the leg and boom, wheels on the ends of said axles, a variable length force applying unit pivoted at one end to the boom and at the other end to the leg and substantially completely housed within the channel shape of the boom, braking surfaces on the boom wheels, and non-rotatable brake operator members movably mounted on the boom axle and operatively engageable with said surfaces to prevent rotation of said Wheels.

15. The invention set forth in claim 14 wherein said braking surfaces are provided by radial slots in the inside faces of said wheels and spaced angularly about the axis of the wheels, said operator members being pivoted on the axle and having noses fitting in said recesses, and overcenter spring means acting between the operator members and the axle to yieldably hold the members in engaged or disengaged positions.

16. In combination with the invention as set forth in claim 12, said force applying means including a manually operated lever, said spring acting as a link between said lever and said 14 ratchet structure, said pressure release element being operated by said lever after predetermined angular movement of said lever.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,945,910 Nilson Feb. 6, 1934 1,956,797 Jackson et a1. May 1, 1934 2,189,010 Lewis Feb. 6, 1940 2,233,745 Nilson Mar. 4, 1941 2,400,316 Page May 14, 1946 2,458,407 Nieterhauser Jan. 4, 1949 FOREIGN PATENTS Number Country Date 342,093 Great Britain Jan. 29, 1931 633,904 Germany Aug. 13, 1938 727,807 France June 24, 1937 

